Tricky T visors.com is the first thought as most will tell you, but I got mine off E-bay it was full face visor replacement for a welding mask, it was shade 5 green, it really looks the part, its thick, strong and the correct color from what I understand. the only issue I have is it curves inward towards the chin, after all the cutting to get it to fit I just managed to get away with chopping 99.9% of the curve off..
Not sure I can post link for e-bay but look up full face mask, shade 5, full visor etc.
A lot of searches can come up with just the little replacement glass for the eyes only..
Hope that helps